The President's decision to use the bully pulpit to start calling political plays from the sidelines has brought the all-Trump, all-the-time mania that has raged through Hollywood, late-night talk shows and the arts roaring into professional sports.

It was probably inevitable, given the way he has seized the nation's psyche since his shock win in last year's presidential election, that the most powerful man in the world would sooner or later turn his attention -- and his volcanic Twitter feed -- toward America's most powerful sports league.

His decision to do so now threatens not just to embroil the NFL in politics for years to come but to reshape the experience of those who watch it.

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Wading into the debate about protests by mostly African-American players during pre-game national anthem ceremonies, Trump is exacerbating questions about his own attitude toward race and his apparent determination to keep tugging at the societal and cultural fault lines in American politics.

He kept up his end of the controversy Monday morning, comparing on Twitter what he saw as the patriotism of NASCAR to the "disrespecting" of the US and its flag. But invoking auto racing -- which is especially popular in the conservative south, the epicenter of Trump's political support -- will do little to quiet the fervor or dispute the suggestion that he is stoking racial tensions. While some of the most prominent players in the NFL and the NBA are black, auto racing has long been viewed as one of the whitest of professional American sports.

'One of the biggest sports stories'

In years past, on any given Sunday, the NFL has offered moments of rare unity in a nation split by politics, economic disparity and race, when the logo on your jersey was more important than whether you came from red or blue America.

The controversy that erupted when Colin Kaepernick, the former San Francisco 49ers quarterback, first took a knee during the national anthem last season to protest a flag he said oppressed people of color has led the league into treacherous political territory.

Now that the President is involved, it's only going to get more fraught.

"There is no doubt this is one of the biggest sports stories and the biggest cultural stories that we have seen in some years," said USA Today sports columnist Christine Brennan on CNN's "Reliable Sources" on Sunday.

Trump's attitude did not come out of the blue.

While supporters of the take-a-knee protests believe the players are exercising their constitutional rights, the President was speaking for other Americans, many on the right, who see the whole thing as unpatriotic. And his willingness to speak up will strike many of his most loyal supporters as validation for their vote for the most unconventional politician in modern American history last fall.

Football is not the first area of national life to experience the turbulence stirred by Trump's status-quo rattling election victory last year.

The President's unique, politically incorrect style has injected a jolt of resistance into late-night talk shows -- with comedians like Jimmy Kimmel leading a campaign to save Obamacare. Alec Baldwin's dark take on Trump has meanwhile helped drive the political conversation and returned the glory years to NBC's "Saturday Night Live."

In another sign of the disconnect between the former reality show star and the showbiz world that he once courted, Trump is skipping the annual Kennedy Center Honors ceremony in December after top artists threatened a political backlash.

Even as he reserved his deepest scorn for the NFL, the President's capacity to draw everyone within shouting distance into his web of controversy was obvious Sunday as he left the National Basketball Association, Major League Baseball and the National Hockey League with public relations headaches.

Going to the White House is considered a great honor for a championship team.Stephen Curry is hesitating,therefore invitation is withdrawn!

The NHL's Pittsburgh Penguins for instance, found themselves on the end of a Twitter battering from some fans after Trump tweeted that the Stanley Cup winners accepted an invitation to visit him in the White House, hours after he had rescinded an invitation to the NBA champion Golden State Warriors, following criticism from the team's star player Stephen Curry. Protests also seemed to be spreading to baseball.

Trump's political play-by-play

Trump's wild weekend all started at an Alabama rally on Friday, when he said an NFL owner should fire any "son of a bitch" player who knelt during the national anthem.

By Sunday, his comments had changed the way the game is covered.

Pre-game shows, normally pulsating with chalk talk, instead probed the political implications of race and protest.

Sports politics, once waged by pioneers like Muhammad Ali and Jackie Robinson, but now largely confined to tussles between multi-millionaire players and multi-billionaire owners, suddenly became consumed once more by questions of civil rights, freedom, and what it means to be an American.

Throughout the day, the President kept up his own political play-by-play, amazingly calling for a boycott of the league.

"If NFL fans refuse to go to games until players stop disrespecting our Flag & Country, you will see change take place fast. Fire or suspend!" Trump tweeted.

If NFL fans refuse to go to games until players stop disrespecting our Flag & Country, you will see change take place fast. Fire or suspend!

Trump's succession of explosive interventions on the NFL was so surreal it even eclipsed the President's flippant threat to wage nuclear war in North Korea -- against the "little Rocket Man" Kim Jong Un, in the United States at least.

His shots at the NFL appeared to be an attempt to separate the players from team owners and the fans from their Sunday afternoon obsession.

Yet, just as his bluster has not stopped Kim's quest for a nuclear weapon, his outspoken remarks seemed to spark more defiance among NFL players, officials and owners than sympathy.

Dozens of players knelt on one knee, or locked arms, as the anthem singers belted out the Star-Spangled banner.

Some teams refused to take the field at all for the pre-game ceremonies.

Trump's friend, Robert Kraft, the owner of the New England Patriots, who gave him a Super Bowl ring, meanwhile said he was "deeply disappointed" by the President's tone. And the protest even reached Wembley Stadium in London, where the Jacksonville Jaguars were playing the Baltimore Ravens.

NFL Commissioner Roger Goodell, under fire over the league's handling of domestic violence perpetrated by players and brain injuries, meanwhile seized the chance to capture the moral high ground.

But Trump refused to back down.

"Well I think the owners should do something about it. I think it's very disrespectful to our flag and to our county," Trump said on Sunday evening.

His blast at the NFL players came as he waged a separate feud with several top NBA stars.

"It's not what leaders do," said Curry. In another remarkable moment, the NBA's top star LeBron James took to Twitter to brand Trump a "bum."

U bum @StephenCurry30 already said he ain't going! So therefore ain't no invite. Going to White House was a great honor until you showed up!

For Trump's critics, his swipes at prominent African-American sports stars is simply a evolution in what they see as a deeply suspect position on race, following his "Birther" crusade against former President Barack Obama and his failure to swiftly condemn white supremacists after violence in Charlottesville.

But the President insisted on Sunday that he's simply standing up for the flag as he voices sentiments that he says are felt deeply by many people, who he says are turned off that football has been entwined with political statements.

"I've never said anything about race. This has nothing to do with race or anything else. This has to do with respect for our country and respect for our flag," Trump told reporters Sunday.

Critics of the take a knee protests argue that the issue is about the constitutional right to protest but amounts to defaming a flag that has been a poignant rallying point for US service personnel and first responders in the decade-and-a-half of war since 9/11.

"This is not about Republicans or Democrats," said Treasury Secretary Steven Mnuchin on CNN's "State of the Union."

"Players have the right for free speech off the field. On the field, this is about respect for lots of people."